From: Mike Snitzer Subject: [PATCH v5 1/2] block: skip elevator data initialization for flush requests Date: Fri, 4 Feb 2011 11:58:39 -0500 Message-ID: <20110204165839.GA2630@redhat.com> References: <20110201185225.GT14211@htj.dyndns.org> <1296600373-6906-1-git-send-email-snitzer@redhat.com> <20110202225549.GA28109@redhat.com> <4D4AAC9A.4050407@fusionio.com> <20110203133820.GF2570@htj.dyndns.org> <20110204150456.GD32190@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Tejun Heo , Vivek Goyal , "tytso@mit.edu" , "djwong@us.ibm.com" , "shli@kernel.org" , "neilb@suse.de" , "adilger.kernel@dilger.ca" , "jack@suse.cz" , "linux-kernel@vger.kernel.org" , "kmannth@us.ibm.com" , "cmm@us.ibm.com" , "linux-ext4@vger.kernel.org" , "rwheeler@redhat.com" , "hch@lst.de" , "josef@redhat.com" , "jmoyer@redhat.com" To: Jens Axboe Return-path: Content-Disposition: inline In-Reply-To: <20110204150456.GD32190@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org Skip elevator initialization for flush requests by passing priv=0 to blk_alloc_request() in get_request(). As such elv_set_request() is never called for flush requests. Signed-off-by: Mike Snitzer --- block/blk-core.c | 29 +++++++++++++++++++++++++---- 1 file changed, 25 insertions(+), 4 deletions(-) v5: introduces blk_rq_should_init_elevator() to abstract the elevator initialization decision to promote future reuse and clarity. Index: linux-2.6/block/blk-core.c =================================================================== --- linux-2.6.orig/block/blk-core.c +++ linux-2.6/block/blk-core.c @@ -753,6 +753,25 @@ static void freed_request(struct request } /* + * Determine if elevator data should be initialized when allocating the + * request associated with @bio. + */ +static bool blk_rq_should_init_elevator(struct bio *bio) +{ + if (!bio) + return true; + + /* + * Flush requests do not use the elevator so skip initialization. + * This allows a request to share the flush and elevator data. + */ + if (bio->bi_rw & (REQ_FLUSH | REQ_FUA)) + return false; + + return true; +} + +/* * Get a free request, queue_lock must be held. * Returns NULL on failure, with queue_lock held. * Returns !NULL on success, with queue_lock *not held*. @@ -764,7 +783,7 @@ static struct request *get_request(struc struct request_list *rl = &q->rq; struct io_context *ioc = NULL; const bool is_sync = rw_is_sync(rw_flags) != 0; - int may_queue, priv; + int may_queue, priv = 0; may_queue = elv_may_queue(q, rw_flags); if (may_queue == ELV_MQUEUE_NO) @@ -808,9 +827,11 @@ static struct request *get_request(struc rl->count[is_sync]++; rl->starved[is_sync] = 0; - priv = !test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags); - if (priv) - rl->elvpriv++; + if (blk_rq_should_init_elevator(bio)) { + priv = !test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags); + if (priv) + rl->elvpriv++; + } if (blk_queue_io_stat(q)) rw_flags |= REQ_IO_STAT;